


Mirror Image

by fangirlingtodeath513



Category: Supernatural
Genre: Accidental meeting, Castiel/Dean Winchester First Kiss, Fluff, M/M, Mirror Universe, Old Castiel (Supernatural), Physicist Dean Winchester, Professor Dean Winchester, Scientist Dean Winchester, Time Travel
Language: English
Status: Completed
Published: 2020-04-07
Updated: 2020-04-07
Packaged: 2021-03-01 17:42:42
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,707
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23521018
Author URL: https://archiveofourown.org/users/fangirlingtodeath513/pseuds/fangirlingtodeath513
Summary: Castiel's had this entire universe to himself for as long as he's been here. He doesn't even know how long it's been since he's seen another living person.That is, until a beautiful green-eyed man shows up in his garden.
Relationships: Castiel/Dean Winchester
Comments: 25
Kudos: 145





	Mirror Image

**Author's Note:**

> Hey guys! Been a hot minute since I've posted anything. This was inspired by The Flash :D
> 
> Thank you to the wonderful [Gii](https://archiveofourown.org/users/heylittleangel/pseuds/heylittleangel) for beta reading this fic for me <3

“Hello?”

It’s been a long, long time since Castiel has heard another voice in person, though he’s not entirely sure that this  _ is _ in person. His focus  _ had _ slipped, perhaps he was accidentally watching someone’s house again. With a weary sigh, he rises to his feet and follows the voice.

He has to blink a few times to make sure what he’s seeing is real. He’s been here entirely alone with only glimpses of the real world for a while, but here’s this real, living, breathing human being standing in his garden. He’s… taller than Castiel remembers, at least based on the glimpses he’d seen through his mirrors. His eyes are the color of the fields in front of his house in the spring and it makes Castiel long for the warmer weather. 

“Hello?” the man asks again, softer this time. Unsure. Castiel can understand that, he’d been more than a little confused when he’d woken up here. Castiel smiles at him, head tilted to the side as he takes in his new companion.

“Hello. How did you get here?”

The man blinks at him, frowning and taking a cautious step back. “You. Who are you?”

He frowns. It’s been a long time since he’s said his human name, long enough that he doesn’t even remember the meaning behind it. Doesn’t remember his mother’s voice when she’d said it, or the first time his fiance had said it—no longer his fiancée, of course, but she’d led a fulfilling life after his disappearance. He’d been happy for her, her eventual husband was a good man.

“Castiel,” he says simply, amazed that he still remembers how to form the word. 

“Castiel,” the man repeats dubiously, his outstretched arm dropping to his side. “Where am I?”

Castiel frowns and tilts his head again. “I’m… not sure how to explain it, to be honest with you.”

The man scoffs. “Well, give it your best shot, then.”

He sighs, clasping his hands in front of himself. “When you look in a mirror… this is what you see.”

The man stares at him like he’s waiting for Castiel to continue, growing more and more frustrated when Castiel remains silent. “What the hell does that mean, man? How do I get out of here?”

Castiel almost winces, but he thinks better of it. The man’s already agitated, telling him that he’s stuck here isn’t going to help anything. “This is a… different universe, if you will. A mirror of your—our—universe. I’m not sure how it was created, but it’s been here for…. Centuries, at least. Maybe millennia.”

“And that’s how long you’ve been here?”

Castiel smiles softly. “No. I was born in seventeen eighty-three.”

The man’s jaw drops as he gives Castiel a once-over. “You don’t look a day over twenty-five, dude.”

“Because I’m not,” Castiel explains with a shrug. “On my wedding day, as I was getting ready, I… something happened. There was this… odd flash of light, a bright red. I woke up here.”

The man frowns. “The same thing happened to me. Well, not the wedding thing, but yeah, red light, mirror, whole shebang. And you’re just… stuck here? You’ve been stuck here for, like, 250 years? How are you still alive?”

Castiel hums. “Time doesn’t move the same way here. I watched my friends, my family, my… my fiancée. I watched them live their lives, I watched them all fall in love and have families and spread their roots until they were happy. I watched them die. I’ve watched centuries change and regimes rise and fall. I’ve watched births and deaths and the rise and fall of countries.” The  _ alone _ remains unsaid, but the man seems to understand. Castiel clears his throat and gives himself a moment to compose himself before continuing, “What were you doing before you came here?”

The man watches him for a moment, almost curiously, before ducking his head and sighing. “That story needs alcohol. Do you have alcohol here?”

Castiel smiles. “I do.” He inclines his head toward the house in the distance and the man seems to get the idea, following a few steps behind Castiel as they walk toward the house Castiel’s made his own. 

“I’m Dean, by the way,” he says, smiling softly as Castiel turns to look at him. 

“It’s nice to meet you, Dean.”

His visitor is silent as he looks around Castiel’s house, a curious kind of silence. No, curious isn’t the right word, Dean seems… excited, almost. Giddy.

“What do you drink?”

Dean smiles. “Whiskey, if you have it.”

Castiel nods and pours a glass, passing it to Dean before pouring himself a glass of wine. He settles into the armchair near the window, indicating for Dean to tell his story. He does, although only after taking a large sip of whiskey.

“I’m a quantum physicist,” he explains, clearing his throat and settling onto the couch opposite Castiel. “Basically I spend—spent, I guess—my life figuring out how things work. All the atoms and particles and everything that makes up the universe.”

Castiel raises an eyebrow. “How does that lead to you being here?”

He smiles almost wistfully and swirls the whiskey around in his glass. “My specialty was mirror particles, basically particles that were opposites of existing particles. It’s what I wrote my thesis on and what all of my research projects have been focused on. They’ve only been theoretical though, at least until now.” Dean shakes his head as he looks around, a small smile on his lips. “I always thought a place like this existed, but I never thought I’d actually prove it.”

Most of those words don’t make sense to Castiel, but he figures he can ask in due time. After all, Dean’s stuck with him now, they’ve got all the time in the world. “How does that lead you to being here, though?”

“I, uh…” he sighs and runs a hand through his hair. “My latest experiment was an attempt to isolate mirror particles in one area and evacuate everything else and I actually managed it. Well, at least I  _ thought _ I had. The moment I touched them, I ended up here, like they were a portal to another dimension or something.” He huffs a laugh. “Guess they kinda were.”

Castiel frowns. “You were  _ experimenting _ with this dimension? Because you thought it  _ might _ exist?”

Dean rubs the back of his neck, a slight blush coloring his cheeks as he blushes. “I-I… yeah, I guess. It’s my job, man, I was supposed to prove this and then write a paper to advance science or whatever. I didn’t think I’d get sucked into an alternate dimension.” He frowns, visibly deflating as he sets his whiskey in front of him on the coffee table. “Man, Sammy’s gonna be so worried.”

Castiel raises an eyebrow. “Is she your wife?”

Dean snorts. “No, dude, my little brother. Sam. He hates when I call him Sammy, but it’s a hard habit to break.” He shrugs. “I was supposed to go to his house for dinner tonight, he and his fiancée were having an engagement party for the family. I can’t believe I’m gonna miss it.”

Castiel frowns. “I fear you may have already missed it, Dean. I told you, time works differently here. I only seem to have aged a decade or so but I’ve been here for over two hundred years.”

Dean sighs and leans back in his chair with a frown. “Shit, Sam’s probably middle-aged already. There’s no way to go back to when you left? If it’s an alternate dimension, maybe we’re outside of time-space.”

Castiel blinks at him. Most of that sentence floats right over his head and Dean seems to recognize that.

“Oh, right, sorry, um… so, think of it as two bubbles that are connected. The place where they’re touching is where we fell through to this dimension. But you’ve said time runs differently here so, theoretically, if we’re able to nudge the bubbles a little bit, we may be able to get back to our dimension around where I left. Or, I suppose, theoretically, around when  _ you _ left. If we nudged the bubbles enough, of course.” Dean pauses long enough to look up at Cas, who has a deep frown etched into his face. “What?”

“You think you can get us out of here? Why? I’ve been stuck here for centuries, Dean, don’t you think I’ve tried everything?”

Dean frowns. “I wasn’t suggesting that, Cas. I’m just saying, I got here on purpose, maybe I can get us out of here the same way. If I could just reverse my experiment… is there a lab nearby, do you know? A science lab?”

Castiel hums thoughtfully. “I think there’s a university nearby? The University of Kansas, I think. I’m still a little shaky on the whole backward-reading thing. Is that significant?”

Dan laughs. “Yeah, dude, that’s where I worked. That’s where I did my experiment. I assume as things happen in the real world, they’re mirrored here, which means everything for my experiment should already be set up.” He grins at Cas, downing his whiskey in one gulp and standing up, clapping his hands together before holding one out to Castiel. “You ready to go back to the real world, Castiel?”

Castiel hesitates, only for a moment, but Dean notices. He withdraws his hand and sits back down, though only on the edge of the couch. “You want to stay?”

“I don’t know,” Castiel admits, tugging the sleeves of his sweater down over his hands, eyes downcast. “I’ve been here so long… your world has changed _so_ _much_ since I left… I don’t know that I’d fit in there anymore. Maybe I’m better off here, maybe I was _meant_ to be here.”

Dean frowns. “You can’t actually believe that, Cas. Isn’t it lonely?”

Castiel shrugs, taking a sip of his wine. “I’m used to it. I’ll be fine.”

Dean wants to argue with Castiel, wants to prove that he’ll be better off in the real world, but it’s not his place. Hell, he’s known Castiel for all of, what, an hour? It’s not up to him whether the other man decides to stay or leave.

Decision made, he thanks Cas quietly and heads for the university. 

It takes him a while to get there, but at least he knows his way around. Cas is living in the town Dean had grown up in, so getting to the university from there is easy.

His lab is exactly how he left it, which is a weird sight. All his equipment looks abandoned and dusty like someone had shut the door to that room and left it there after Dean’s disappearance; maybe they had. He finds his notes easily enough though, tucked in his desk drawer. Problem is, they’re backwards. How the hell is he supposed to read them like this?

It takes some maneuvering and a hell of a lot of practice over what feels like weeks before he’s finally able to decode the information he needs and tweak it for this universe. It takes another couple of days to set the mirror of his original experiment up, but, once he does, he’s good to go. He hesitates, mind drifting back to Castiel as it has so often these last few weeks. He doesn’t want to leave Castiel here, especially if his experiment really works like he thinks it will. Castiel will be stuck here,  _ again _ , alone, for God only knows how long.

“Dean?”

Dean’s head snaps up and he grins as he sees Castiel standing in front of him, hands nervously toying with his shirt. “Cas. You came.”

“I thought about what you said,” he admits with a shrug. “I don’t want to be stuck here alone again. If this even works, that is.”

Dean puts a hand over his heart. “You wound me, Cas. You forget, I’m the one who got here on purpose. I can get us back.”  _ I hope I can get us back _ , he thinks to himself. Not that being stuck here with Castiel would be all that awful, but he misses his home and his friends and family. Not to mention now that Castiel is on board, he actually wants to get them out of here. Cas deserves it.

“So how does this work, exactly?”

Dean grins and launches into teacher mode, explaining the basis of the experiment he’d done to get here and how he’d mirrored it to (hopefully) return them to their world. Castiel nods along and smiles, seemingly at Dean’s enthusiasm, which is all kinds of adorable. 

_ Adorable _ ? Where the hell had that thought come from? Not that he’s not open about his bisexuality, but he hadn’t even been thinking about Cas like that, at least not until that thought had crossed his mind. Now he can’t seem to  _ stop _ thinking about it. Shaking those thoughts away, he turns back to his equipment and takes a deep breath before powering it on.

The result is almost instantaneous. The energy in the room shifts and when he flips the final switch, Cas grabs onto his hand and there’s a flash of bright light that forces them both to close their eyes. 

When they open them again, they’re still standing in Dean’s lab and Dean  _ almost _ sighs out his frustration, but Castiel gasps softly beside him.

“It actually worked, I can’t believe it.” Cas picks up the notebook with Dean’s experiment outlined, which Dean can read without a mirror now, much to his relief. Castiel laughs and glances around the room, his hand still warm within Dean’s. “So this is your universe, then? A lot has changed since I disappeared, I can’t wait to see it all in person.”

The door behind them bangs open loudly and a security guard points a flashlight directly in their eyes, barking at them to get out of the lab. Dean raises a hand to block out the light and tugs Cas closer.

“This is private property, you can’t—hey! You’re that professor!”

Dean blinks at the guard—Benny, his nametag reads—and shakes his head while shrugging. “No idea what you’re talking about, man.”

“Professor Winchester, the one who vanished from his lab a couple’a years ago.”

Dean pales. “A couple of  _ years _ ?”

Benny raises an eyebrow. “Yeah, man, it’s 2022. You disappeared in 2020.” He glances between Dean and Cas and then down at their still-joined hands. “Who’s this?”

“That’s… a long story. Look, can I borrow a phone? I should call my brother.”

Benny chuckles. “I can do you one better, he works here. Jus’ passed his office a few minutes ago, he’s still here. C’mon.” 

Benny leads the way down the hallway and Dean and Cas glance at each other before releasing their hands and hurrying down the hallway after him. He leads them down to an office in the law building— _ nice job, Sammy _ —and then up to the third floor. Sam’s office is the corner one, surrounded by windows on one wall and bookshelves on the other. Sam barely glances up, pauses for a moment, and then nearly shoves his desk forward with how quickly he jumps out of his seat.

“Dean? Is that really you?”

“Yeah, Sammy,” he says with a relieved smile, letting his brother pull him into a tight hug. “Back from the mirror universe.”

Sam scoffs as he pulls away, punching Dean’s shoulder. “You’re such a jackass, Dean. You were just supposed to prove it existed, not disappear there for two years.”

“It wasn’t two years,” Cas pipes up, shrugging. “It was only a few weeks for us.”

Sam narrows his eyes at Castiel, which Cas thinks is fair enough. “Sorry, I don’t think we’ve met. I’m Sam.” He offers a hand, which Castiel shakes with a small smile.

“Castiel. It’s a pleasure to meet you.”

Sam looks to Dean, probably for an explanation, but Dean just shrugs. “Right. Well, um… you’re welcome to come stay with us, then. I’m sure Rowena won’t mind.”

Dean grimaces, though it’s almost imperceptible. “Actually, uh, I was kinda hoping to spend the night in my own bed, if that’s still possible.”

“Oh! Of course. You’d already paid it off so I had Charlie do some… finagling so we could pay the taxes on it. Everything’s still running and I’ve been taking care of it, hoping… well, you know. Hang on, let me grab my stuff and I can drop you off.” Sam heads back to his desk and quickly closes up his books and stuffs his papers into his bag, slinging it over his shoulder as he grabs his jacket. “This way.”

Dean turns to follow his brother, pausing when he realizes Castiel isn’t following them. “You coming?”

Castiel smiles shyly. “I wasn’t sure I was invited. I don’t want to be a burden, Dean, I’ll… figure something out.”

Dean rolls his eyes and holds out a hand. “Dude, c’mon, no way I’m throwing you out to the wolves. You can stay with me, I’ve got a spare room.”

Castiel grins and takes Dean’s proffered hand, nodding. “Thank you, Dean. I promise I’ll make it up to you once I figure things out.”

Dean waves him off, leading him out of the building. “You don’t owe me anything, Cas. Promise. Stay as long as you like, alright? There’s no rush. You’ve been in another dimension for two hundred plus years, you can take a little time to get your feet under you again.”

Castiel smiles gratefully and climbs into Sam’s car next to Dean. If Sam notices their joint hands, he doesn’t say anything.

The ride to Dean’s home is tense, though mostly because Castiel has never ridden in a car before and it’s actually quite terrifying. He’s seen all of this through the mirrors, of course, but watching it and actually living through it are two very different things.

Dean’s house is pretty. There’s a place in front that was obviously a garden at one point, though it’s been severely neglected in the two years Dean’s been missing. There’s a large porch on the front of the house, complete with a swing and a cozy chair in the corner that looks perfect for early mornings watching the sunrise. Dean climbs out and waves Castiel toward the house, lingering near the car, undoubtedly to have a word with his brother. Castiel takes the hint, climbing the three steps onto the porch and brushing his hand over the fluffy cushion on the chair.

Dean climbs the steps a couple of minutes later, smiling softly at Castiel as Sam’s car pulls back onto the road. “Sorry about that, he was worried.”

Castiel smiles. “It’s alright. Worried?”

“Yeah, that you were some stranger that was gonna murder me in my sleep.” Dean grins as he unlocks the front door. “I told him you’re a good dude, you’d have the decency to kill me while I’m awake.”

“You’re not incorrect,” Castiel says, smirking when Dean turns to him with wide eyes. 

“Oh, so you snark back. Good to know.” He chuckles to himself as he opens the door and waves Castiel inside, flipping a switch near the door and frowning. “No electricity. Right. I’ll have to call about that in the morning. Uh, one sec, I keep flashlights in the kitchen, hopefully they still work.” He disappears down the hallway, returning a moment later with a flashlight in hand, lighting up the small hallway. “Sorry, I forgot they would’ve turned the electric off. I’ll get it turned on tomorrow.”

Castiel shrugs. “It’s not a problem for me. I never lived with electricity.”

Dean raises an eyebrow. “Not even in the mirror universe?”

“No. I just lived by daylight.”

Dean frowns. “What made you change your mind, anyway? You seemed pretty set on staying.”

Castiel glances at him, biting his lip. “I… There was… I wanted…” He seems to be having a difficult time finishing his sentence, so Dean smiles and stops in front of the door to his guest room.

“Hey, man, don’t worry about it. I was just curious, alright? You don’t have to tell me if you don’t want to.”

Castiel shakes his head and takes a deep breath. “You looked at me like I looked at my fiancée when I met her,” he explains, tilting his head and hoping Dean understands what he’s trying to say. “I thought, maybe… maybe it wouldn’t be so bad if I came back… with you.”

Dean raises his eyebrows, but there’s a hint of a blush high on his cheeks. “Oh, that’s… shit, I’m sorry, I didn’t think you realized. I’m sorry.”

Castiel smiles softly. “Why? Is that… did you mean it that way?”

Dean clears his throat. “Um, I mean… you are very… attractive,” he stammers, rubbing the back of his head. “I’m sorry if that’s, uh, offensive or something. I know back then it was a bad thing, but these days it’s… well,  _ less _ of a bad thing.”

“Same-sex attraction,” Castiel confirms with a small smile. “I know. Sometimes when I was feeling lonely, I would watch people’s weddings. I’ve seen more and more same-sex weddings in the last few months.” He twists his sleeves over his hands, clearing his throat. “I was always… I didn’t… It was never bad. Not to me, at least. I’m sure other people in my time period didn’t accept it, but I was— _ am _ —uh… I don’t know the term for it. My attraction is not limited to females.”

“Bisexual,” Dean supplies, then frowns. “Maybe pansexual? I dunno, that’s a topic we can revisit later. Sorry, I’m sure you’re tired.” He opens the door, sweeping the flashlight beam over the room. “It ain’t much, but we can shuffle things around once we get settled, get your room how you like.”

Castiel smiles brightly. “It’s perfect, Dean. I’m just thankful that I have a place to sleep.”

The corner of Dean’s mouth quirks up in a ghost of a smile and he pulls another flashlight from his pocket, handing it to Castiel. “There’s a button on the end of the handle that will light it up. Bathroom’s across the hall.” He grimaces, glancing at the door across the hall. “Maybe don’t flush unless you need to. Not sure it’ll work without electricity. My room’s at the end of the hallway if you need anything, alright?”

“Alright. Thank you, Dean. I’ll see you in the morning.”

Dean smiles softly and nods, heading down the hallway to his room. 

It’s pure bliss to be back in his own bed, his perfect memory-foam molding to him the minute he touches it. He’s barely able to click his flashlight off before he’s asleep.

It’s weird to wake up to a roommate the next morning. He hasn’t had a roommate since college, but having Castiel around is actually pretty nice. Dean picks them up breakfast sandwiches and they eat on the porch. Castiel opens up about his life before being stuck in the mirror universe and Dean fills him in on what’s happened since he’d disappeared, at least, as well as he can. 

They fall into a comfortable rhythm in the next few weeks. Dean is rehired by the university with the promise that he’ll present his findings about the mirror universe, which he readily agrees to. Cas gets a job at the nearby convenience store and for a while, they’re just like normal roommates, sharing the common areas and having meals together when they’re both home. It seems like it’ll be like that for the foreseeable future, at least until Dean comes home from work one day to an entirely dark house. Cas doesn’t have a shift today, so there’s no reason for the house to be empty. He’s only slightly panicking about someone kidnapping Cas when he unlocks the front door and drops his bag in the entryway, heading straight for the living room.

“Cas? You home?”

He doesn’t get a response, but he does hear quiet shuffling coming from the couch, so he flicks the light on and immediately regrets it when he sees Cas flinch and hug his knees tighter against his chest. 

“Cas? Buddy, what’s wrong?” He crosses the room without thinking, perching on the coffee table and resting a hand on one of Cas’s knees. He’s been crying, that much is obvious, and it breaks Dean’s heart.

“Nothing, I’m sorry. I’m just having a bad day,” he murmurs, sniffling quietly as he lets his legs down. “How was your day?”

Dean sighs. “Man, don’t worry about me. Talk to me, what’s goin’ on?”

Castiel sighs. “I just feel like… maybe I should have stayed behind sometimes. I don’t fit in here and I’m just burdening you with my presence because I couldn’t live on my own and you’d feel bad if you didn’t let me stay here.”

Dean blinks at him for a moment before sitting up and frowning. “Cas, that’s not true. I  _ enjoy _ having you here. I’ve lived on my own for a while, it’s nice to have someone to come home to, even if it’s just to share a meal with or watch a TV show with. And yeah, maybe you don’t exactly fit in, but you’re getting the hang of it. It’s gonna take more than just a couple of months, last time you were in this universe you didn’t even have electricity or indoor plumbing.” He shuffles forward and rests a hand on Cas’s shoulder, smiling reassuringly. “Don’t be so hard on yourself, man. I like having you here and Nora says you’re a great employee. So take your time and adjust, you’re doing just fine.”

Castiel smiles gratefully and wipes his face with his sleeves before pulling Dean into a tight hug. “Thank you. I’m sorry.”

Dean only hesitates for a moment before returning the hug, staunchly ignoring the heat turning his cheeks red. It’s just a crush, he needs to get this shit under control, he doesn’t want Cas to feel uncomfortable living here. “Nothin’ to apologize for, Cas. C’mon, I’ll make us some dinner.”

Castiel takes his proffered hand and follows him to the kitchen, pausing for a moment in the doorway. He tugs Dean to a stop since their still-joined hands won’t let him make it to the fridge with Castiel stopped in the doorway. He raises an eyebrow and turns to glance at Cas, who’s just smiling softly at Dean. “Can I kiss you?”

Dean’s brain grinds to a halt. Did Cas really just ask him that? “I-I, uh… what?”

Castiel shrugs. “You  _ did _ say you thought I was attractive, and I think you are as well. I know I’ve still got a lot to learn about this world, but I just thought… unless you don’t want to?” he finishes, a confused sort of frown on his face. Dean shakes his head and uses their joined hands to pull Cas closer and into a kiss.

It’s heavenly. Cas’s lips are soft and warm and he smiles into the kiss, which makes Dean smile and pull him even closer until their chests are pressed together. Cas’s arms wind around his neck and one hand plays with the short hairs at the base of his head and it’s all Dean can do to keep from skipping dinner and dragging Cas to the bedroom. But no, this isn’t some one-night stand, this is  _ Castiel _ . He wants to do this the right way, so he pulls away after a moment and rests their foreheads together. “I do. I  _ really _ do. But I want to do this the right way. Like, actual dates, walks in the park, the whole thing.”

“Courting,” Castiel answers with a smile, nodding and kissing Dean again. “I’m amenable.”

  
Dean grins. “Yeah? Then let me take you to dinner on Saturday. I know you’re not working and I’ve just got a few more papers to grade, I can have them done before then.”

Castiel’s face lights up with a grin that’s brighter than any sun Dean’s ever seen and he nods. “I’d like that, Dean.” He chuckles and presses a soft kiss to Dean’s jaw. “Maybe it wasn’t such a bad idea to come back with you, after all.”

**Author's Note:**

> Find **this fic** on [Tumblr  
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